1. Field of the Invention
This invention relates to the field of sonic flow meters of the type particularly described as ultrasonic, single-path, transit time flow meters such as described in U.S. Pat. No. 3,720,105. The invention is particularly directed to the field of ultrasonic flow meters having computational apparatus for correcting sonically determined flow rates for viscosity, to provide corrected flow rates.
2. Description of the Prior Art
A convenient and commonly used means of measuring liquid flow is by the use of sonic flow meters. These are devices which transmit sound pulses through the fluid flowing in a conduit. In the most commonly practiced means of employing ultrasonics for measuring fluid flow rate, a sonic path is provided between an upstream and downstream location spaced on opposite sides of a conduit. In the preferred method of practicing the invention the rate of travel of the sound through the liquid is measured in both directions, that is, with the fluid flow component and against the fluid flow component. By subtracting such measurements, which effectively cancels out the rate of sound travel through the fluid itself, the rate of the fluid flow can be accurately determined.
The application of ultrasonic flow meters to measurement of such products as water which change little in viscosity, has been successfully employed. Difficulty, however, is experienced in the use of ultrasonic flow meters to measure volumetric flow rates of fluids which vary considerably in viscosity. This is particularly a problem in attempts to utilize ultrasonic flow meters in the petroleum industry wherein the viscosity of the hydrocarbon fluids varies over a great range.
An object of the present invention is to provide means of utilizing ultrasonic flow meters for measuring the flow rates of fluids having variable viscosities.
Another object of this invention is to provide means employing sonic measurements to determine the viscosity of a fluid flowing in a conduit.
Another object of this invention is to provide means employing empirically derived relationships for calculating corrected flow rates of fluids wherein the measurements required for determining the flow rate are supplied as upstream and downstream sonic measurements along with the fluid temperature measurement.
These general objects as well as other and more specific objects of the invention will be fulfilled in the following description and claims, taken in conjunction with the attached drawings.